As a financial expert, it's crucial to understand the concept of net premiums written. This refers to the total premiums an insurer receives for all policies written within a specific timeframe, regardless of what portions have been earned. However, it's important to note that this figure excludes any premiums written after reinsurance transactions. In other words, it reflects the insurer's true liability and shows the actual amount of risk they are taking on. This is a vital component in evaluating an insurer's financial health and stability.